Schools in much of the US are closed and have been for several weeks, many more like 6 weeks, simply because it's summer. Summer camps etc. are going on, but those are usually smaller groups and often outdoors. And more likely to be sorted by social status, which probably reduces mixing between vaccinated and unvaccinated households.
This bit of the US has also been vaccinating kids over 12 for a couple of months, with 3-4 weeks between shots.